The world is full of diversity. Organisms may be different colors, have different shapes, or have different behaviors, so how could they be considered similar? The answer lies in their core, where they are all constructed of DNA. DNA, also known as deoxyribonucleic acid, is the molecule that codes for the genetic material of organisms, controlling how they function and develop. It is a double helix structure made of nucleotides, consisting of a phosphate group, a sugar group, and a nitrogen base.
Genes are made of DNA, and “genomes” are the sum total of an organism’s DNA. The appearance and function of an organism is determined by the genome, as the genome holds all of the instructions for both its creation and maintenance. There are four types of DNA nucleotides: cytosine, guanine, adenine, and thymine. Genome sequencing is figuring out the order of these nucleotides in an organisms’ DNA. By comparing the genome sequences of different species, one can observe both the genetic similarities and differences.
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Based off of outward appearance, a chimpanzee and human seem rather similar. From their opposable thumbs to intelligence, the two bear many of the same traits. Thus, one would think that a chimpanzee and a human would be similar in DNA. Sure enough, a comparison of their genomes reveals that humans and chimpanzees share about 98% of the same DNA. However, biology is not about judging a book by its cover. Just because two species do not look alike does not mean that they are not alike in genetics.
If one were to put a human and a mouse side by side and compare based off of appearance alone, that person would say that they do not look alike. Despite this, there is more that lies beyond the surface. A comparison of their DNA and genome sequencing will reveal just how actually similar they are. They share several DNA blocks, insinuating that they are biologically related, and evolved from a common ancestor. Interestingly, the human strand appears to contain all of the blocks, whilst the blocks are scattered among different strands in the mouse. From this, a researcher can assume and conclude that once, many, many years ago, they shared a similar origin that eventually evolved into two completely separate species, but traces of the old ancestor can still be tracked using compared genomes. In conclusion, the average percentage of identical protein-coding regions between mice and men is around 85%.
Mice and humans sharing DNA not only works as a fun fact, but is also very helpful in the scientific field. It is used especially in the testing aspect of things. For example, let’s say a scientist has possibly found a cure for a disease, but is not completely sure without running trials. It would be considered immoral and inhumane to test it on a human due to its unpredictability with a human life, so scientists found a solution with lab rats. This has to do with the fact that humans and rats share DNA, so the effects on a rat would presumably apply to a human. The scientists get to see the results of their experiment without the worry of a human life on their hands thanks to genomic similarities.
This concept of genomic comparisons does not just apply to animals either. Take a banana, for example. A frequently heard fun fact is that bananas share some genetic code with humans, ranging from around 40 to 60 percent. However, humans do not have a peel or a bright yellow color. Then how can this be explained? Well, genes do not simply code for appearance. It also controls the inner functions that may not be visible to the bare human eye. For example, two completely separate species could share the same gene for cell growth, and “share 60% of DNA.” Comparing genomes, one can find similarities that they would have never been able to guess before.